There is a chance one user will unintentionally override someone else's changes if they update a record near the same time. One solution is to use optimistic locking. The updated_at column can also be used for this as shown.
(8 minutes)

The strong_parameters gem is an improvement over attr_accessible to securely handle mass assignment even when you have complex authorization logic. The functionality will likely be added to Rails 4 so it is a good idea to learn how it works.
(12 minutes)